1. Field of the Invention
This invention relates to air- and water-impermeable coverings for roofs or the like. More particularly, it relates to a roofing system employing for its air- and water-impermeable covering a plurality of elongated sheets of marginally edge lapped covering material and, in which, the sheets are designed to be adhesively or cohesively sealed together along their elongated marginal edge portions, as well as sealed to flashing or the like at appurtenant structures, either at the perimeter of or intermediate the perimeter of the surface to be covered. Specifically, the invention relates to the making and/or repairing of a roof or the like, in which, there are laid down on the surface to be covered a plurality of elongated sheets of heat-sealable roofing material, in overlapping relationship and, in particular, it relates to a method for finishing the seams between the above-mentioned sheets themselves, as well as between the sheets and chimneys, skylights, vent pipes, perimeter walls and the like, and to a device which is particularly suited and useful for the seam-finishing practice mentioned above.
2. Description of the Prior Art
In the making of a roof for a structure which has either a flat or low-sloping roof, there are generally at least three major systems that have been employed most extensively in the United States.
First, there are the asphalt (or "tar") and gravel roofs which are made with several alternating (or built-up) layers of roofing felt, each coated with hot- or cold-mopped asphalt. The roofing felt provides a water-resistant membrane sandwiched between the roof's sheathing and its surface. Made from wood fibers and recycled paper that have been saturated with asphalt oils, roofing felt prevents moisture, such as rain, from penetrating and damaging the sheathing. The uppermost layer of mopped felt is then generally surfaced with crushed rock or gravel (ballast). As recently as about ten years ago, roofs made by this cumbersome and time-consuming practice comprised nearly all of the flat or low-sloping roofs in the United States.
Second, there is the more recent practice of making rubber roofs, wherein elongated sheets of rubber are laid in suitable overlapping relationship, with the joints between the laps and elsewhere, where water penetration might occur, being provided with an elastic cement or an adhesive composition. Here, once again, a final layer of gravel or the like may be used, if desired.
Third, and more pertinent to the present invention, there is the approach wherein the surface to be covered is provided with a weatherproof membrane comprised of a plurality of sheets of a modified-bitumen-containing, heat-sealable roofing material. It is known to those skilled in the art how to make such roofing material, an example of which is "KMM" membrane manufactured and marketed by Koppers Company, Inc. of Pittsburgh, Pa. The Standard KMM membrane, for example, is a five-layer laminate composed of a thick, flexible, plastic core protected on each surface by a layer of modified bitumen material and an outer film of polyethylene.
Moreover, the prior art contains numerous suggestions of methods for roofing with heat-sealable roofing material of the type mentioned above. Generally, these methods include depositing, in edge-overlapping relation, on a surface to be roofed, such a heat-sealable roofing material and, then, with the use of an apparatus which lifts the overlapping portion between adjacent sheets, applying heat in the form of gaseous combustion products to the gap therebetween to an extent sufficient to allow the contact surfaces to be fused or sealably joined and, finally, pressing the heated contact surfaces together with sufficient force to sealably join the overlapping edge portions of the material. Examples of such disclosure and such equipment may be found in U.S. Pat. Nos. 2,084,625; 4,087,309; 4,204,904; 4,239,581 and 4,259,142 the disclosures which are incorporated herein by reference.
A further example of a device for applying such heat-sealable sheet material to a roof or other flat or nearly-flat surface area may be found in U.S. Pat. No. 4,354,893, the disclosure of which is also incorporated herein by reference. In accordance with this last-mentioned disclosure, a device is provided which applies, from a plurality of jets located in a row adjacent to the entire width-wise underside of the sheet being laid down, hot gases resulting from the combustion of hydrocarbon fuel, usually gaseous fuel, to said underside of the roofing material, thereby causing it to become tacky and adhesive to the surface portions with which it is substantially immediately thereafter brought into contact.
In the making of a roof with such heat-sealable or modified-bitumen-containing roofing material, there exists, as a usual and desirable step, an operation of finishing the seams that exist between the sheets of roofing material thus laid down. Though it is possible to omit this step, considering the roof finished either when the sheets of material have been laid down or after the subsequent application of a layer of gravel or the like, it is generally preferable or desirable to conduct a finishing operation, i.e., one in which oozed-out material is directed back into each seam between two overlapping sheets of heat-sealable roofing material. Conducting such a step is particularly important, whether or not a final layer of gravel is to be used. Experience reveals that, in such a seam between two sheets of heat-sealable roofing material, some parts of the seam have oozed-out material adjacent thereto and others do not. The places that do not, if nothing is done, afford places of weakness in the roof, i.e., locations in which, for example, the wind may work upon a location where the two sheets are not in contact and increase the extent of the area not in contact, a factor which is conductive to the ultimate failure of the roof.
Also, seams may occur in such roofing construction in zones or areas characterized by the presence of chimneys, skylights, vent pipes, building perimeter walls and the like. These additional seam zones or areas also require thorough sealing or finishing due to the same considerations as set forth above, i.e., separation of the roofing material occurring at the seam, causing ultimate failure of the roof through, for example, the ravages of wind, ice or rain.
Although the foregoing cited patents relate to the same general subject matter as the instant invention, namely, the laying of roofs of modified-bitumen-containing material or the like, they are not concerned with exactly the same problem that provides the focal point of this invention and they do not teach or suggest how it may be overcome. They are specifically more concerned with either applying heat to the overlapping edge portions of the sheets or applying heat to the sheet underside substantially throughout its width (i.e., U.S. Pat. No. 4,354,893) to get a good initial seal, rather than, as herein, to effecting the finishing of a defective seal, once made, by substantially uniformly redistributing therealong oozed-out material or adding additional material, so that no place exists along the seam that affords a place of weakness where, as aforesaid, wind or other forces may cause sheet separation and ultimate failure of the roof.
Perhaps the most important consideration in roofing is that there be obtained a roof which does not leak, either initially or after an extended period of service. Adequately performing a seam-finishing step, throughout the length of each seam, is an important safeguard toward obtaining the desired result, and this is true whether or not the seam edges are later to be protected from wind attack by the application of an overlying layer of gravel or the like. The tool and the method of the present invention, as well as that of applicant's co-pending application Ser. No. 728,808 filed Apr. 30, 1985, are useful for obtaining with a minimum of time, effort and cost, such an adequate seam-finishing operation, particularly for the laying of roofs of modified material which has, in its installation, been heated on its underside substantially throughout its width, for example, with a device of the kind more particularly shown in the U.S. Pat. No. 4,354,893, mentioned above. It is also believed that the approach of U.S. Pat. No. 4,354,893 necessarily gives better results, in respect to obtaining a leak-proof roof, than any method or device which involves merely the lifting and fusing of an edge portion of each lap, as taught in such references as U.S. Pat. No. 2,084,625, mentioned above.